I think it's a very nice Vassal module - good right click functionality for the units. I've only played 1 scenario solitaire (scenario 1) so other might want to chime in. However from my perspective if you're waiting to buy the game due to uncertainty on the vassal module I'd say go ahead and get it.
I eagerly await delivery. I may do a blog-like thing on it, Vassal is easier. And I'll likely play it far more on Vassal as well.